Nanolevitation Phenomena in Real Plane-Parallel Systems Due to the Balance between Casimir and Gravity Forces

Abstract

We report on the theoretical analysis of equilibrium distances in real plane-parallel systems under the influence of Casimir and gravity forces at thermal equilibrium. Due to the balance between these forces, thin films of Teflon, silica, or polystyrene in a single-layer configuration and immersed in glycerol stand over a silicon substrate at certain stable or unstable positions depending on the material and the slab thickness. Hybrid systems containing silica and polystyrene, materials which display Casimir forces and equilibrium distances of opposite nature when considered individually, are analyzed in either bilayer arrangements or as composite systems made of a homogeneous matrix with small inclusions inside. For each configuration, equilibrium distances and their stability can be adjusted by fine-tuning of the volume occupied by each material. We find the specific conditions under which nanolevitation of realistic films should be observed. Our results indicate that thin films of real materials in plane-parallel configurations can be used to control suspension or stiction phenomena at the nanoscale.

Premelting of ice adsorbed on a rock surface

“…[56] This repulsive frequency range then has to dominate the influence from an eventual other attractive frequency range in order to make the force repulsive. [57,51,53,58,59,60,14,37,61,62,63,64,65] The transition distance from attractive to repulsive Lifshitz force occurs when the attractive and repulsive frequency contributions exactly cancels. [53] Pioneering studies of liquid helium films on different substrates have in the past clearly shown the effect of repulsive Lifshitz forces.…”

van der Waals torque and force between anisotropic topological insulator slabs

“…[26], the non-retarded limit of the vdW free energy for isotropic TIs ( ⊥ = z ≡ ) can be deduced from Eqs. (12) and (21) of the paper. In our notation, their result takes the form…”

“…The search for repulsive Casimir/vdW forces is circumscribed by the existence of a no-go theorem, which states that the Casimir/vdW force in a mirror-symmetric setup is always attractive [9][10][11]. In the context of conventional dielectric media, one way to evade the theorem and generate a repulsive vdW force between two coplanar layers across a gap of a different material is to have the dielectric permittivities increase (or decrease) across the layers [7,12,13]. However, such a scenario does not apply to systems involving a pair of dielectrics separated by a vacuum gap, which are the systems that would be relevant to device application [6].…”

Trapping of Gas Bubbles in Water at a Finite Distance below a Water–Solid Interface

“…The Lifshitz (van der Waals) forces that are at play in a system like the one here proposed, can be either attractive or repulsive as was known already to the pioneers . 7 This has been demonstrated many times both theoretically [8][9][10][11][12][13][14][15][16][17] and experimentally 4,18-25 in a variety of schemes. What is more fascinating is the fact that equilibrium between repulsive (downward) Lifshitz forces and attractive (upward) buoyancy might cause stable trapping of gas bubbles under water-solid interfaces at distances easily accessible experimentally.…”